The most important thing in boycotts is not giving them (more) money, and not promoting their goods/services. You can't get your money back from already bought things, so you can use or buy used stuff from other person.
Regarding Minecraft, the most effective is to avoid all its subscriptions and new purchases. But there are more actions, like not promoting and not playing. It is more about what you can do at the moment. Usually, listening and sharing the bad things done by the company helps you decide what can you do rn.
If you knew someone is doing terrible stuff with the goods/services you are offering to them, would you happily continue to have that commercial relationship?
Israel crimes are known. Microsoft has deleted accounts for muuuuuuuuuuch less.